Communication devices such as wireless terminals are also known as e.g. User Equipments (UE), mobile terminals and/or mobile stations. Wireless terminals are enabled to communicate wirelessly in a cellular communications network or wireless communication network/system, sometimes also referred to as a cellular radio system or cellular network. The communication may be performed e.g. between two wireless terminals, between a wireless terminal and a regular telephone and/or between a wireless terminal and a server via a Radio Access Network (RAN) and possibly one or more core networks, comprised within the cellular communications network.
Wireless terminals may further be referred to as mobile telephones, cellular telephones, laptops, tablet computers or phablets with wireless capability, just to mention some further examples. The wireless terminals in the present context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the RAN, with another entity, such as another wireless terminal or a server.
The cellular communications network covers a geographical area which is divided into cell areas, wherein each cell area being served by a base station, e.g. a Radio Base Station (RBS), which sometimes may be referred to as e.g. “eNB”, “eNodeB”, “NodeB”, “B node”, Base Transceiver Station (BTS), depending on the technology and terminology used. Hereafter, base stations in the cellular communications network is in general referred as cellular network access nodes, which comprising Second/Third Generation (2G/3G) network access nodes, 3G Long Term Evolution (LTE) network access nodes, Worldwide interoperability for Microwave Access (WiMAX) network access nodes, etc.
Nowadays, almost all wireless terminals are equipped with a wireless local network unit, such as a Wireless Local Area Network (WLAN) unit. A wireless local network which may be a part of a wireless communications network, provides a connection for a wireless terminal through an access point to the Internet usually with high bandwidth and low cost. It gives users of the wireless terminal the mobility to move around within a local coverage area and still be connected to the wireless local network. The access point in the wireless local network is referred hereafter as a wireless local network access node.
Rapid growth in data traffic driven by mobile applications on wireless terminals such as smart phones, tablets and the like has continued to strain the capacity of the wireless communications network. To provide the best experience for the users of the wireless terminal regarding quality of service, mobility, security, cost and speed etc., switching or handover between different access nodes, e.g. between a cellular access node and a wireless local network access node is usually performed.
The conventional way of going over from a cellular network, e.g. a 3rd Generation Partnership Project (3GPP) network to a wireless local network, e.g. the WLAN is when the signal strength of a WLAN access node is higher than a predefined threshold. The problems of such an approach are possible degradation of the performance, Ping-Pong effect between the WLAN and 3GPP network access nodes, and negative impacts on other wireless terminals already connected to the WLAN. For example, when a wireless terminal enters into a public place, where the wireless local network access node has good radio condition, e.g. the signal strength is high, but there are many users already connected to the access node and have active sessions, handover to this access node will degrade the performance of the communications for this wireless terminal and have negative impacts on other users already connected to this access node. For another example, when a wireless terminal enters into an area where the signal strength of a wireless local network access node is around the predefined threshold. If the wireless terminal moves around, the signal strength will change between above or below the predefined threshold during a short time. This will consequently cause Ping-Pong effect between the cellular network access node and the wireless local network access node.